North Korean workers assemble clothing at the South Korean-run ShinWon garment factory at the Kaesong industrial complex on Sept. 21, 2012, in Kaesong, North Korea. North Korea barred South Korean managers and vehicles from entering the industrial park on April 3, a day after announcing it will restart its nuclear program. Jean H. Lee, AP

The Kaesong industrial complex is visible from the Dora Observation Post on May 26, 2010, near Panmunjom, South Korea. The North-South industrial park began producing goods in 2004. Lee Jin-man, AP

People entering North Korea fill out forms at the Inter-Korean Transit Office on April 3 in Paju, South Korea. There are 800 South Koreans, most of them managers, working at the industrial park. Jung Yeon-Je, AFP/Getty Images

South Korean vehicles entering Kaesong wait at the customs, immigration and quarantine office on Feb. 13. There are 120 South Korean companies operating factories in Kaesong. Lim Byung-shik, AP

North Korean workers bundle wires at a South Korean-run factory on April 3 in Kaesong. The factories provide jobs for 50,000 North Korean workers who produce textiles, clothing and electronic components. Jean H. Lee, AP

A U.S. Army soldier watches South Korean vehicles return from North Korea on March 28. Ahn Young-joon, AP

A South Korean manager, left, consults with North Korean workers at the ShinWon garment factory on Sept. 21, 2012, at the Kaesong industrial complex. Jean H. Lee, AP

A South Korean car arrives at a military checkpoint on April 3 at the inter-Korean transit office. Jung Yeon-Je, AFP/Getty Images

A worker directs South Korean vehicles returning from Kaesong at the customs, immigration and quarantine office in Paju. Factories at the industrial park produce $470 million of goods that are trucked back to South Korea for export to other countries. Ahn Young-joon, AP